EP0321670A2 - Expansion valve control device for the refrigerating appliance of a motor vehicle air conditioning equipment - Google Patents

Expansion valve control device for the refrigerating appliance of a motor vehicle air conditioning equipment Download PDF

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Publication number
EP0321670A2
EP0321670A2 EP88117426A EP88117426A EP0321670A2 EP 0321670 A2 EP0321670 A2 EP 0321670A2 EP 88117426 A EP88117426 A EP 88117426A EP 88117426 A EP88117426 A EP 88117426A EP 0321670 A2 EP0321670 A2 EP 0321670A2
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EP
European Patent Office
Prior art keywords
refrigerant
evaporator
temperature
expansion valve
t2
Prior art date
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Granted
Application number
EP88117426A
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German (de)
French (fr)
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EP0321670A3 (en
EP0321670B1 (en
Inventor
Roland Burk
Hans-Joachim Ingelmann
Karl Lochmahr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mahle Behr GmbH and Co KG
Original Assignee
Behr GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE19873743285 priority Critical patent/DE3743285A1/en
Priority to DE3743285 priority
Application filed by Behr GmbH and Co KG filed Critical Behr GmbH and Co KG
Publication of EP0321670A2 publication Critical patent/EP0321670A2/en
Publication of EP0321670A3 publication Critical patent/EP0321670A3/en
Application granted granted Critical
Publication of EP0321670B1 publication Critical patent/EP0321670B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B41/00Fluid-circulation arrangements, e.g. for transferring liquid from evaporator to boiler
    • F25B41/06Flow restrictors, e.g. capillary tubes; Disposition thereof
    • F25B41/062Expansion valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B2341/00Details of ejectors not being used as compression device; Details of flow restrictors or expansion valves
    • F25B2341/06Details of flow restrictors or expansion valves
    • F25B2341/065Electric expansion valves
    • F25B2341/0652Electric expansion valves being opened and closed cyclically, e.g. with pulse width modulation
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B2600/00Control issues
    • F25B2600/21Refrigerant outlet evaporator temperature
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B2700/00Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21Temperatures
    • F25B2700/2117Temperatures of an evaporator
    • F25B2700/21174Temperatures of an evaporator of the refrigerant at the inlet of the evaporator
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B2700/00Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21Temperatures
    • F25B2700/2117Temperatures of an evaporator
    • F25B2700/21175Temperatures of an evaporator of the refrigerant at the outlet of the evaporator
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70Efficient control or regulation technologies
    • Y02B30/72Electric or electronic refrigerant flow control

Abstract

A device for controlling the expansion valve (5) of a refrigerating appliance in a motor vehicle is described. A first temperature sensor (22) measures in a first place the temperature (T3) of the refrigerant in the direction of flow behind the evaporator (10); a second temperature sensor (20) measures in a second place the temperature (T2) of the refrigerant in the direction of flow in front of the evaporator (10). A controlling variable is derived from this, which serves for adjustment of the expansion valve (5) in such a manner that there is a given superheating of the refrigerant overflowing into the compressor (1). It is envisaged that a further temperature sensor (21) is arranged in the refrigerant circuit. In this connection, two temperature sensors (20, 21) are to be situated in the wet steam region (X) in all operating states, so that a pressure drop takes place between them. The superheating of the refrigerant overflowing into the compressor (1) is determined from the temperatures (T1, T2, T3) determined with the temperature sensors, of which there are three in total. The controlling variable (4) is derived from this. <IMAGE>

Description

  • The invention relates to a device for controlling the expansion valve of a refrigeration device further comprising a compressor, evaporator and condenser in a motor vehicle, in which a first temperature sensor at a first point the temperature of the refrigerant downstream of the evaporator and a second temperature sensor at a second point the temperature of the refrigerant in the flow direction in front of the evaporator and a manipulated variable is derived therefrom, which is used to adjust the expansion valve in such a way that a specific one specified overheating of the refrigerant passing into the compressor downstream of the evaporator is given.
  • Such devices are known. Depending on the measured temperatures, the expansion valve is controlled in such a way that there is always a certain, but not excessive, "optimal" overheating of the refrigerant. This is to ensure that only gaseous refrigerant is supplied to the compressor following in the direction of flow, since otherwise proper functioning would not be guaranteed. On the other hand, for reasons of an optimal cycle, one is interested in having to accept as little overheating as possible at the outlet of the evaporator.
  • One could now make the measurement of the state of the refrigerant after the evaporator or before the compressor more reliable by measuring the pressure of the refrigerant after the evaporator instead of the temperature of the refrigerant before the evaporator and deriving the manipulated variable for the expansion valve from temperature and pressure . However, pressure gauges are much more expensive than temperature gauges.
  • However, the determination of the condition of the refrigerant or its overheating based on the temperature measurements before and after the evaporator has proven to be unreliable. This is especially true when it comes to the Actuation of the expansion valve of a refrigeration device in a motor vehicle, whose operating parameters, in particular the refrigerant pressure at the evaporator outlet, change constantly as a result of the constant changes in the operating conditions of the motor vehicle, in particular the engine speed which is decisive for the performance of the compressor.
  • The invention is therefore based on the object of improving the determination of the superheating of the refrigerant before entering the compressor as an output variable for controlling the expansion valve of a refrigeration device in a motor vehicle on the basis of temperature measurements.
  • According to the invention, this object is achieved in that a further temperature sensor is arranged at a further point in the refrigerant circuit and measures the temperature of the refrigerant, such that two temperature sensors are in the wet steam range in all operating states and there is a pressure drop between them, and that the overheating occurs of the refrigerant flowing into the compressor is determined from the temperatures determined with the three temperature sensors and the manipulated variable for the expansion valve is derived.
  • The indication that a total of two temperature sensors should be arranged at locations between which there is a pressure drop and which in all operating conditions in the Wet steam range ensures that saturation temperatures are always measured. As is known, in the enthalpy-pressure diagram, the wet steam area is the bell-shaped area within which the refrigerant is present as a two-phase system, that is to say both as a vapor and as a liquid.
  • In principle, the two points can be arranged along the length of the evaporator or between the expansion valve and the evaporator, provided that there is a certain pressure drop between them, for example also in front of and behind the vortex cell and / or the venturi distributor. Pressure drop occurs at both. The arrangement in the flow direction upstream and downstream of the venturi distributor has proven to be particularly advantageous. The venturi distributor, which divides the refrigerant flow flowing to the evaporator over several evaporator tubes, acts practically like a measuring orifice.
  • The mathematical determination of the overheating after the evaporator or before the compressor, the precise control of which is dependent on the setting of the expansion valve, is carried out when measuring temperatures at three points which satisfy the specified conditions, in such a way that the overheating (Δtü) results from the by means of the three temperature sensors measured temperatures (T₁, T₂, T₃) in a computing unit according to the formula
    Δtü = T₃-T₂ = k (T₁-T₂) (1)
    is calculated, where k is an evaporator-specific constant that is unique experimentally according to the relationship
    Figure imgb0001
    must be determined, the boiling temperature T'₃ is to be determined by a pressure measurement and conversion via the refrigerant-vapor pressure relationship. On the basis of the value for Δtü and relationship (1), the manipulated variable is then determined in such a way that the overheating always has the specific predetermined value. Based on this differential temperature determination and calculation, a manipulated variable for the expansion valve can then be derived in a manner known per se by a computing unit. For example, if the overheating is too great, the evaporator is underfilled with liquid. The degree of opening of the expansion valve, which is controlled by actuators known per se, is increased in this case until the desired overheating, calculated from the measured temperatures, occurs again, etc.
  • An embodiment of the invention and its advantageous developments is described below with reference to the accompanying drawings. It represent
    • 1 shows the refrigerant circuit of a cooling device in a motor vehicle with the associated measuring and control devices;
    • Figure 2 shows the real course of the cycle in the enthalpy-pressure diagram and
    • 3 shows the course of the temperature before and along the length of the evaporator.
  • The cooling device according to Figure 1 consists of compressor 1, line 2, condenser 3, line 4, expansion valve 5, which is clocked by a solenoid 6, line 7, venturi distributor 8, several lines 9, evaporator 10 and line 11. As shown by the Arrows indicated, air flows through both the condenser 3 and the evaporator 10. The air flowing through the condenser 3 cools it. On the other hand, the air flowing through the evaporator is cooled by the evaporator. The condenser is usually exposed to the wind, while the evaporator is traversed by the air to be cooled in the interior of a motor vehicle.
  • Along the refrigerant circuit, three temperature sensors 20, 21, 22 are arranged, which measure the temperatures T₁, T₂, T₃. The temperature sensor 20 is located in line 7 in front of the venturi distributor 8. The temperature sensor 21 is located on one of the lines 9 behind the venturi distributor 8. The lines 9 are all passed through the evaporator 10 after the refrigerant flow in the venturi distributor 8 has been divided into equal partial flows is. The temperature sensor 22 is located behind the evaporator 10, that is to say in front of the compressor 1.
  • The course of pressure and temperature at the individual points of the refrigerant circuit results from the illustration of the cycle in FIG. 2, the reference numerals being attached to the individual straight lines, which correspond to those structural units according to FIG. 1 in which the changes in state represented by the straight lines are shown perform. The following information serves to explain this cycle process, but is only to be understood as an example:
  • At the end of line 11 there is, for example, a pressure of 2.5 bar at 8 ° C. The pressure in the compressor is increased to 18 bar at 100 ° C. In line 2 and in condenser 3, the temperature is lowered and the refrigerant is converted into the liquid phase, with a slight pressure drop. At the beginning of line 4 there is, for example, 16 bar at 55 ° C. The pressure drops very sharply in the expansion valve 5 and in the adjoining line 7. At the same time, as a result of the drop in pressure, part of the refrigerant changes its physical state from the liquid to the gaseous phase, as a result of which the refrigerant cools to the lower temperature T₂, the rest of the liquid phase evaporates in the evaporator 10 by removing heat from the surroundings, so that a temperature of 5 ° C can be given at the outlet of the evaporator at a pressure of about 3 bar.
  • The solid and bell-like curve X, drawn somewhat thicker than the other lines, describes the wet steam area, i.e. the area in which, under the condition conditions of the coolant defined thereby, it is present both in the vapor phase and in the liquid phase.
  • Of great importance for the correct functioning of the compressor 1 is that there is a certain overheating Δtü before its input. Overheating refers to the fact that the temperature is higher than the temperature at which the coolant changes from the liquid phase to the gaseous phase. The greater the overheating, the safer the refrigerant is in the gaseous phase. For reasons of operational safety, a temperature must be given at the input of the compressor 1 which can be expected with certainty that the entire refrigerant is in the gaseous phase, that is to say has completely evaporated. Is this e.g. not the case, i.e. if the temperature is lower, this means that too much refrigerant has entered the evaporator. The expansion valve must e.g. controlled by clocking so that less refrigerant passes through. The temperature behind the evaporator or before the refrigerant enters the compressor then becomes correspondingly higher.
  • The arrangement of the temperature sensors 20, 21, 22 is shown in FIG. 2 also designated by the reference numerals 20, 21, 22. Through these points in the cycle, the dashed isotherms T₁, T₂ and T₃ go. It can be seen that, as mentioned, the temperature sensors 20, 21 are inside the curve X and the temperature sensors 22 are outside the curve X.
  • The lower, dashed line in Figure 3 is undesirable because it provides a temperature T'₃ too low. The upper of the two courses delivers a temperature T₃, which is higher by the desired amount Δtü.
  • It has now been found that the temperature Δtü can be calculated very reliably from the temperatures measured by the sensors 20, 21, 22 at the specified points using the following formula
    Δtü-T₃-T₂ + k (T₁-T₂).
    k is a constant that depends on the design of the evaporator. The size k is determined in the manner already outlined and ultimately represents the ratio of the refrigerant-side pressure drop in the evaporator tube to the comparative pressure drop of the measuring orifice. With regard to sufficient measuring accuracy, the measuring point for T 1 and T 2 should be arranged such that the constant k is approximately 1 at least but within the limits 0.5 ≦ k ≦ 1.5. she will experimentally determined for each of the specific cooling devices and then used as a basis for the calculation of Δtü. The calculation is carried out in the computing unit 30 (see FIG. 1) to which the temperatures T 1 to T 3 measured by means of temperature sensors 20 to 22 arrive. A manipulated variable y = f (Δtü) is then derived in the computing unit 30. A corresponding control signal is, for example, a sequence of rectangular pulses of a certain length. The length and the distance of the rectangular pulses determine the temporal relationship between opening and closing of the expansion valve 5, so that the amount of coolant passing through the expansion valve is controlled in this way.

Claims (3)

1. Device for controlling the expansion valve (5) a further compressor (1), evaporator (10) and condenser (3) having refrigeration device in a motor vehicle, in which a first temperature sensor (22) at a first point, the temperature (T₃) Refrigerant in the flow direction behind the evaporator (10) and a second temperature sensor (20) at a second point measures the temperature (T₂) of the refrigerant in the flow direction in front of the evaporator (10) and a manipulated variable is derived from it, which is used to adjust the expansion valve (5 ) is used in such a way that there is a certain predetermined overheating (Δtü) of the refrigerant passing into the compressor (1) downstream of the evaporator (10), characterized in that a further temperature sensor (21) is arranged at a further point in the refrigerant circuit and the temperature (T₂) of the refrigerant measures, such that there are two temperature sensors (20,21) in all operating conditions in Naßdam pf range (X) and there is a pressure drop between them, and that the overheating (Δtü) of the refrigerant passing into the compressor (1) from the temperatures determined with the three temperature sensors (20, 21, 22) (T 1, T 2, T 3) ) is determined and the manipulated variable (4) for the expansion valve (5) is derived from it.
2. Apparatus according to claim 1, characterized in that the two locations in the wet steam area are arranged in the flow direction upstream and downstream of the venturi distributor (8), which divides the flow of refrigerant flowing to the evaporator (10) over several evaporator tubes.
3. Apparatus according to claim 1, characterized in that the overheating (Δtü) from the measured by means of the three temperature sensors (20,21,22) temperatures (T₁, T₂, T₃) in a computing unit (30) according to the formula
Δtü = T₃-T₂ + k (T₁-T₂)
is calculated, where k is an evaporator-specific constant.
EP19880117426 1987-12-19 1988-10-19 Expansion valve control device for the refrigerating appliance of a motor vehicle air conditioning equipment Expired - Lifetime EP0321670B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE19873743285 DE3743285A1 (en) 1987-12-19 1987-12-19 Device for controlling the expansion valve of the refrigeration device in a motor vehicle air conditioning
DE3743285 1987-12-19

Publications (3)

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EP0321670A2 true EP0321670A2 (en) 1989-06-28
EP0321670A3 EP0321670A3 (en) 1990-05-23
EP0321670B1 EP0321670B1 (en) 1992-07-22

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5186021A (en) * 1991-05-20 1993-02-16 Carrier Corporation Bypass expansion device having defrost optimization mode
WO1996012148A1 (en) * 1994-10-15 1996-04-25 Danfoss A/S Control arrangement for the superheat temperature of at least one evaporator of a refrigeration system
EP2137471A4 (en) * 2006-12-29 2015-05-06 Carrier Corp Air-conditioning control algorithm employing air and fluid inputs

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB639683A (en) * 1947-11-07 1950-07-05 J & E Hall Ltd Improvements in apparatus for the control of expansion valves of refrigerators
US3478534A (en) * 1967-08-11 1969-11-18 Controls Co Of America Thermistor controlled refrigeration expansion valve
US3538717A (en) * 1968-12-04 1970-11-10 Controls Co Of America Refrigeration system control arrangement including heat motor operated expansion valve
EP0133512A2 (en) * 1983-08-06 1985-02-27 Joh. Vaillant GmbH u. Co. Refrigerant flow control for a heat pump
US4617804A (en) * 1985-01-30 1986-10-21 Hitachi, Ltd. Refrigerant flow control device
US4653288A (en) * 1984-07-02 1987-03-31 Hitachi, Ltd. Apparatus for measuring refrigerant flow rate in refrigeration cycle
US4689968A (en) * 1986-03-21 1987-09-01 Danfoss A/S Actuator means for the control of a refrigeration system expansion valve

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3659783A (en) * 1969-10-24 1972-05-02 Eaton Yale & Towne Temperature regulated flow control element for automotive air-conditioners
DE2530021C3 (en) * 1975-07-04 1980-07-31 Fiat S.P.A., Turin (Italien)
CA1087412A (en) * 1976-03-04 1980-10-14 Charles D. Orth High side pressure limiting thermostatic expansion valve
DE3220420A1 (en) * 1982-05-29 1983-12-15 Westfael Elekt Werke Process for the regulation of an electrically controllable expansion valve
JPS61256153A (en) * 1985-05-08 1986-11-13 Toyoda Automatic Loom Works Air conditioner for car
DE3601817A1 (en) * 1986-01-22 1987-07-23 Egelhof Fa Otto Control device for the refrigerant flow for evaporating refrigeration systems or heat pumps and expansion valves arranged in the refrigerant flow

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB639683A (en) * 1947-11-07 1950-07-05 J & E Hall Ltd Improvements in apparatus for the control of expansion valves of refrigerators
US3478534A (en) * 1967-08-11 1969-11-18 Controls Co Of America Thermistor controlled refrigeration expansion valve
US3538717A (en) * 1968-12-04 1970-11-10 Controls Co Of America Refrigeration system control arrangement including heat motor operated expansion valve
EP0133512A2 (en) * 1983-08-06 1985-02-27 Joh. Vaillant GmbH u. Co. Refrigerant flow control for a heat pump
US4653288A (en) * 1984-07-02 1987-03-31 Hitachi, Ltd. Apparatus for measuring refrigerant flow rate in refrigeration cycle
US4617804A (en) * 1985-01-30 1986-10-21 Hitachi, Ltd. Refrigerant flow control device
US4689968A (en) * 1986-03-21 1987-09-01 Danfoss A/S Actuator means for the control of a refrigeration system expansion valve

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5186021A (en) * 1991-05-20 1993-02-16 Carrier Corporation Bypass expansion device having defrost optimization mode
WO1996012148A1 (en) * 1994-10-15 1996-04-25 Danfoss A/S Control arrangement for the superheat temperature of at least one evaporator of a refrigeration system
EP2137471A4 (en) * 2006-12-29 2015-05-06 Carrier Corp Air-conditioning control algorithm employing air and fluid inputs

Also Published As

Publication number Publication date
EP0321670A3 (en) 1990-05-23
DE3743285A1 (en) 1989-06-29
EP0321670B1 (en) 1992-07-22

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